Graphical user interfaces (GUIs) are commonly employed in connection with microprocessor-based computing devices to edit digital documents (e.g., word processing documents, images, etc.). Many of these computing devices (e.g., Tablet PCs, PDAs, cell phones and the like) attempt to provide a natural and expressive way to annotate documents with free form digital ink via a digital pen, mouse, etc. Ideally, utilizing such devices should feel like writing on physical paper, and the resulting annotation should appear similar to its ink counterpart. Thus, a goal of such computing devices is to provide a surface that emulates physical paper.
However, a variety of ergonomic factors make it difficult to fully achieve this goal. Examples of such factors include: slip; resolution; screen size; parallax; and device size and weight. Slip generally refers to the fact that pen-computing devices tend to be more slippery than real paper. Resolution takes into account that digital screens have less visual resolution than paper. In addition, digitizers usually track digital pens at lower resolution than the finest human hand movements. Parallax is a consequence of providing a protective layer of plastic over the screen, wherein the protective layer creates an apparent displacement between the tip of the digital pen and underlying document. Size and weight, including screen size, reflects design considerations for portable devices that result in devices and screens that are often smaller than standard letter-size paper and more difficult to position and interact with.
While hardware designers continue to improve pen-based devices to make them feel more like paper, a substantial gap remains. Many limitations associated with these devices force users to change the way in which they interact with such devices and annotations often end up appearing very different from ink on paper. In particular, screens associated with such computing devices are usually smaller than a sheet of paper. Conventional techniques for fitting at least a portion of a page within a screen include adjusting the display resolution and/or “zoom.” However, these techniques involve scaling down text and/or graphics, which can render the document information unreadable. In addition, many devices can be hardware and/or software limited such that selecting a higher resolution is not an option. Another problem with scaling down text and/or graphics is that the user typically ends up annotating at a much larger size than they would on paper. The large size of the ink generally results in annotations that are less dense than real ink annotations on paper, consume limited screen real estate, obscure the underlying document, and appear clumsy.
Conventional techniques that attempt to address writing scale versus display scale fail to emulate physical paper. For example, in many of these techniques, the user specifies a focus cursor in a main overview area at the top of the screen. Then, the user writes in a focus area at the bottom of the screen, wherein the annotations are reduced to a predefined percentage (e.g., 40%) of the original size and placed at the focus cursor. Upon filling the focus area, the user typically is required to perform a right to left movement in the focus area in order to move the focus cursor forward. With other techniques, the focus area constantly scrolls from right to left, thereby continuously clearing space for new annotations. Still with other techniques, the user is required to explicitly create new writing space when filling the focus area, which can break the flow of writing, or modify their writing style to work with the continuous scrolling writing area.
Conventional techniques that employ zooming usually magnify a region of interest within an image or document such that the surrounding context is not visible after the zoom. Navigating in the zoomed view typically requires scrolling, which can be tedious when the magnification factor is high. Other approaches include a multi-scale view of the document, in which a magnified focus region shows details while the surrounding context remains visible. Navigation through the document is typically achieved by positioning a focus region (or lens) over the underlying document, for example, via panning and/or zooming. Although many conventional techniques attempt to provide a natural and expressive way to annotate documents and images with freeform digital ink (via a digital pen, mouse, etc.) these techniques do not overcome the aforementioned problems with annotating on small-screen devices like Tablets PCs, PDAs, cell phones and the like and fail to emulate writing on physical paper.